It is well known that the components (modules) mounted on circuit packs contained within an enclosure require cooling. Typically, this is accomplished by employing a fluid heat carrier (gaseous or liquid) which passes over and around the components so as to remove their excess heat. The heat carrier, most often atmospheric air, is supplied to the cavity within the enclosure via an inlet. The heat carrier is permitted to reach the individual components where it absorbs their excess heat and, thereafter, is removed via an outlet typically located opposite from the inlet. The motion of the heat carrier is typically forced, either by injecting it at the inlet or employing suction to remove it from the outlet.
Historically, in the design of circuit packs, little or no consideration was given to the implications of component placement on cooling efficiency. Primary consideration instead was given to routability and manufacturability of the circuit pack. As a consequence, components were placed indiscriminantly on the circuit board regardless of their aspect (height to width) ratio or size. Such placement typically resulted in poor removal of heat from the components comprising the circuit packs. Indeed, such placement could result in a further convective heating of particular components as they were subjected to heat carried to them by the heat carrier which had already been removed from other components. Such poor removal of heat or excessive heating can cause premature component failure.